22、Choose three

Which three are true about dropping columns from a table?

A) A column can be removed only if it contains no data.

B) A column drop is implidtly committed

C) A column that is referenced by another column in any other table cannot be dropped.

D) A column must be set as unused before it is dropped from a table.

E A primary key column cannot be dropped.

F) Multiple columns can be dropped simultaneously using the ALTER TABLE command.

source:cuug